1. Field of the Invention
This invention relates to photography and, more specifically, to the simulation of real lighting conditions.
2. Description of Related Art
There are numerous situations when the lighting in a scene needs to be duplicated.
One such situation is when the scene is photographed separately from the subject. In this situation, the photographs of the subject and the scene must be composited. A realistic composite usually requires the subject to be lit as if the subject was in the scene, including all of the spatial variations in the light that are present at the location in the scene at which the subject is to be inserted.
This is a challenging task. It is made even more challenging by the fact that many scenes have complex spatial variations in their light. Examples include a forest, cathedral, museum or candlelit hut. Making the composite look as though the subject is actually in such a scene is particularly difficult with complex subjects such as the human face. Adding to the difficulty is the fact that viewers are extremely sensitive to the appearance of people""s faces.
It is also often desirable to make a subject appear as though it were in the lighting provided by a particular scene, even though the subject is not composited with that scene. For example, it is sometimes useful to make a cultural artifact appear as though it was present in a complex lighting environment, such as a cathedral.
Unfortunately, existing technologies are not able to realistically simulate the complex lighting that is often present in a scene on a subject that is not in that scene.
One object of the invention is to obviate this as well as other problems in the prior art.
Another object of the invention is to make a subject appear as though it was being lit by the complex lighting in a scene-including the colors, intensities and spatial directions of light in that scene-even though the subject was never in that scene.
Another object of the invention is to realistically simulate the casting of scene lighting on a perspective of a subject that is not present in the scene that is different from perspectives of the subject that have been photographed.
Another object of the invention is to make a subject appear as though it was lit by the complex light in a virtual scene.
These as well as still further features, objects and benefits of the invention are obtained by a lighting simulation process and apparatus that simulates the lighting of a subject at a location in a scene.
In one embodiment, scene illumination data is created. The scene illumination data specifies the illumination that the scene provides at the location at which the subject is to be simulated from a plurality of spatial directions. Subject illumination data is also created. The subject illumination data specifies the appearance of the subject when illuminated from a plurality of different spatial directions. The subject is then rendered illuminated as if at the location in the scene by combining the scene illumination data with the subject illumination data.
In one embodiment, the scene illumination data specifies both the intensity and color of the illumination from each of a plurality of spatial directions.
In one embodiment, the rendering is accomplished by separately multiplying the value of each pixel in the subject illumination data for each spatial direction by the illumination value in the scene illumination data from that same spatial direction and summing the results over all of the spatial directions.
In one embodiment, each pixel contains values specifying both its color and intensity.
In one embodiment, the subject illumination data is created by illuminating the subject with a small light directed toward the subject from a first spatial direction; photographing the appearance of the subject under the illumination of the light from the first spatial direction; illuminating the subject by a small light directed towards the subject from a second spatial direction different from the first spatial direction; and photographing the appearance of the subject under the illumination of the light from the second spatial direction. In one embodiment, the two last steps that were just recited are repeated for additional spatial directions, each different from all of the others, until the totality of spatial directions from which the subject is illuminated and photographed approximates evenly-spaced locations on a sphere or dome.
In one embodiment, the small light is substantially white in color.
In one embodiment, a single light source is used to illuminate the subject from each spatial direction, and the light source is successively moved to illuminate the subject from each spatial direction after each photographing.
In one embodiment, the light source is moved in a spiral path.
In one embodiment, the spots of light are generated by an array of sequentially-fired light sources mounted on an arm that rotates around the subject.
In one embodiment, the subject illumination data specifies the appearance of the subject from a single view point.
In one embodiment, the subject illumination data specifies the appearance of the subject from a plurality of different viewpoints. In one embodiment, the subject is rendered from a viewpoint that is different from any of the viewpoints specified by the subject illumination data. This is accomplished by extrapolating from the viewpoints that are specified by the subject illumination data.
In one embodiment, the subject includes a human face.
In one embodiment, the subject includes a cultural artifact.
The invention also includes subject illuminating data gathering apparatus for creating subject illumination data used in a lighting simulation process for simulating the lighting of the subject at a location in a scene.
In one embodiment, the lighting apparatus sequentially illuminates the subject with a small light from a sequence of different spatial directions. A camera takes a photograph of the subject when illuminated from each spatial direction. A recorder records each photograph and information indicating the spatial direction from which the subject was illuminated at the time of each photograph.
In one embodiment, the lighting apparatus includes a light and movement apparatus that moves the light to each spatial direction. In one embodiment, the moving apparatus moves the light in a spiral path.
In one embodiment, the lighting apparatus includes an arm, a plurality of lights mounted on the arm, location apparatus connected to the arm that rotates the arm, and a strobing circuit that sequentially fires each light on the arm as it rotates.
In one embodiment, the arm is semi-circular.
In one embodiment, the spatial directions substantially approximate evenly-spaced locations on a sphere or dome.
In one embodiment, the small light is substantially white.
In one embodiment, the subject illumination data gathering apparatus includes a plurality of cameras, each for taking a photograph of the subject when illuminated from each spatial direction from a viewpoint different from the viewpoints photographed by the other cameras.
In one embodiment, the recorder also records information indicative of the identity of the camera that took each photograph.
In one embodiment, the lighting apparatus includes a plurality of strobe lights and a D.C. power supply for supplying pulses of D.C. power to the strobe lights.
In one embodiment, the subject illumination data gathering apparatus includes subject-stabilizing apparatus for helping the subject remain still during the photographing. In one embodiment, the subject-stabilizing apparatus includes a headrest.
The invention also includes computer-readable media containing computer programming instructions which, when loaded in a computer system, cause the computer system to render a subject illuminated as though at a location in a scene by combining subject illumination data specifying the appearance of the subject when illuminated from a plurality of different spatial directions with scene illumination data specifying the illumination that the scene provides at a location at which the subject is to be illuminated from a plurality of spatial directions.
These as well as still further features, objects and benefits of the invention will now become apparent from a review of the following detailed description of illustrative embodiments and the accompanying drawings.